DE2942434A1 - CIRCUIT ARRANGEMENT FOR TELECOMMUNICATION CONNECTIONS - Google Patents

Description

PFENNING MAAS MEINIB Mockery Patent attorneys KurfOrstendamm 170, D 1000 Berlin 15

6527-A

Your reference

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PATENTANWÄLTE BERLIN ■ MUNICH

J. Planning, OpI -tag O I Mm *. Oipl -Chem Munich

IC H Meinig, Dipl -Phys Berlin Dr. G. Spott, Oipl -Chem Munich

Approved agents at European Patent Office OFFICE BERLIN: I Kurfürstendamm 170 I D 1000 Berlin 15 Phone: 030/8812008/8812009 Telegrams: Cable defense patent Telex: 52 15880 Our sign Bertin Our reference Date

18th October 1979

NIPPON TELEGRAPH & TELEPHONE PUBLIC CORPORATION
1-6, üchisaiwaicho 1-chome, Chiyoda-ku, Tokyo, Japan

Circuit arrangement for telecommunication connections

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The invention relates to a circuit arrangement for telecommunication connections according to the preamble of claim 1.

Speech channel circuits or line switching arrangements of the type of interest here are used in the present case Invention seen in connection with an electronic telephone keypad, for example with a corresponding telecommunication control circuit, a distribution system or the like, wherein the The present circuit particularly relates to a speech channel switching arrangement and the speech channel can be controlled directly by the energy fed in from the telephone system, with the telephone system may be a central office or a PBX telephone device or the like.

The comparable electronic devices used so far are characterized by only a small telephony switching capacity with respect to the speech channel circuit, whereby for the Push-button switch PNPN transistors or diode switching elements or C-MOS transistor circuits with analog electronic switching devices were used.

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Examples of such facilities previously used and the electronic ones used in them Switching elements are shown in FIGS. 2 and 3, these speech channel circuits corresponding to the State of the art electronic switching elements with high damping and correspondingly high losses operate, as is the case with C-MOS switching transistors. The last according to the state of the art The illustrated embodiment with electronic switching elements uses PNPN transistors or switching diodes, which are suitable for controlling the speech stream so that it is either blocked or is let through.

In order to be able to understand the problems given with the present circuit arrangements more easily, a prior art is described below with reference to FIG. 1, which is a telephone keypad or a telecommunications control circuit operated in which no electronic switching elements Find application. As can be seen from Fig. 1, the circuit arrangement contains an ordinary control device for the telephone system 1 with the incoming central exchange lines 2a, a push button or

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Keypad 3 of a telecommunications control circuit 4, with the local lines 2b and central exchange line selection switches 5a, 5b, 5c and 5d. The exchange input lines 2a to the common control device I. and the communication setting circuit 4 are connected to the selection switches 5a to 5d of the central office line via the local lines 2b. In diesel The embodiment is the direct current resistance, also called double-line or loop resistance, which resides in the central control device 1 with respect to the input lines 2a, equal to the sum the resistances of a line cable, namely here the local lines 2b between the common Control device 1 and the telephone keypad 3 and the internal resistance of the telecommunication setting circuit 4 (total sum of the resistance of a transmission element, the resistance of the winding of a converter J or transformer and the voltage drop of a circuit with reversed polarity have corresponding equivalents caused thereby Resistance). In Japan, said loop resistance is prescribed to the effect that it is below 220 ohms must be, since the maximum value of the line resistance to a telephone exchange with 1500 ohms is mandatory and for a holder of a

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Telephone connection with non-standard conditions there is a need to switch the telephone system in Telephone office to be interpreted in such a way that it is ensured for the current, namely for the response current, that can perceive via a relay or the like line element in compliance with the regulations that a telephone subscriber has either picked up the handset of a set to speak or not Appropriate precautions must be taken here.

For this reason, it is not possible to use a connection device, namely one with a simple one Switching capacity, in connection with a telephone line of a telephone connection owner to be used if the internal DC resistance is below a value of 220 Ohm, or with In other words, it is impossible for such a switch to reduce the internal DC resistance below this value. This difficulty also lies with the aforementioned electronic keypad devices that use electronic switching elements.

The general problem, as it applies to the internal resistance of telephone systems, in particular

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of keypad systems, are available, for example, in the article "Development of the Pushbutton Telephon" Set "in the journal" Electrical Communication Laboratories Technikcal Journal "," Vol. 17, No. 11 on pages 2539, 1968, where it is stated that the internal resistance is usually is equal to the sum of 90 ohms and an equivalent resistance of 70 ohms, the 90 ohms through the Transmission resistance plus the resistance given by the converter winding arise, and the equivalent resistance of 70 ohms given by the voltage drop of a bridge rectifier which gives the injected current the polarity defined for the circuit (MFO). In which The latter circuit (MFO) is one that generates an encrypted dual multi-frequency signal generated. In detail, the voltage drop through two diodes of the total of four diodes of the bridge rectifier caused with a voltage of 1.4 V, the current through a Line flows, the resistance of which is 1500 Ohm at 20mA, so that the equivalent resistance is derived from the The quotient of 1.4V / O, O2A = 70 Ohm results. If the Loop resistance of 40 ohms is added to the aforementioned 90 + 70 ohms, the result is a

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Total resistance of the common switching or control device 1 from the input of the central Trunks 2a viewed from 200 ohms.

The telecommunication system shown in Fig. 1 is insofar not usable for electronic switching elements, as far as satisfactory adjustment and control are concerned when the loop resistance is less than 220 ohms.

If, for example, the selection switches 5a to 5d of the central exchange line are replaced by electronic switches then it becomes impossible to make the desired setting in the required manner can. For example, a C-MOS switch has a resistance of around 100 ohms when it is in is in its conductive state, i.e. it is switched through, and accordingly they are state-of-the-art Elements corresponding to the technology have a resistance of about 80 ohms, so that they meet the given requirement for the resistance of the circuit below 220 ohms can not meet satisfactorily. Quite in general, a C-MOS transistor cannot be used for a voice channel circuit because its Breakdown voltage is small, namely around 10V

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is, which results in a correspondingly small current capacity, namely of about 20mA, while how mentioned above, the on resistance is high. From this it follows that it is not possible for the application as switching elements C-MOS-Transisto ren to use.

In the embodiment shown in Fig. 2, the selection switches 5a to 5d of the central exchange line are gated switches within the common Control circuit 1. In FIG. 2, the reference numerals given there correspond to the individual Components those of Fig. 1. The circuit includes a central trunk transformer 6a, a Local line transformer 6b and C-MOS transistor switching elements 7b and an energy source E for Delivery of the speech stream to the keypad 3 of the exchange. With this circuit arrangement, to set the internal resistance to 220 ohms as seen from the central exchange line 2a, a transformer 6a is used, with a resistor for the primary winding of this transformer is set below 220 ohms. Accordingly, for the purpose of reducing the loss the C-MOS transistor switches 7a and 7b have an impedance

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transformation achieved by the secondary winding of the transformer 6a in order to correspond accordingly to reduce the equivalent loss, whereupon the impedance is transformed back, so is brought to the original value by the secondary winding of the transformer 6b so that coincidence with the impedance of the setting circuit 3 is given. No further explanation is required that the Spcechkanalschaltkreis used according to FIG. 2 with C-MOS transistors in different ways is modifiable.

The circuit arrangement shown in Fig. 2 is disadvantageous in that it is an interruption the power supply by the conventional power source the electronic keypad with respect to the the setting made interrupts the conversation.

To remedy this situation, it is necessary to have an auxiliary power source in addition to the supply line " provide, for example, a reserve or emergency battery, so that the electronic dialing system of the phone does not break down even if the normal power supply fails, which is currently happening

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then offers if circuits are used with the modern low energy consumption Components are populated. If, however, what must be assumed, a telephone device by means of Battery operation over several hours or even over a power of ten for a longer period of time must, then it is necessary to use a battery with a correspondingly large capacity, about 10 or even several hundred ampere hours to be assigned to the system, which is not insignificant in terms of costs and volume increased, and in addition, it is not always easy to keep this battery in the to keep charged state, which is associated with additional monitoring.

Where a PNPN transistor switching element is used takes place with a turn-on resistor whose value is less than an order of magnitude than a C-MOS transistor ^) rs then it is not necessary to transform the impedance of the circuit by means of a transformer, so that the central input lines 2a are connected to the local lines via the PNPN transistors since the voltage drop across the PN connections is around 0.9V and the equivalent Resistance 4 is 5 ohms for a loop current of 20mA.

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The sum of these resistances and the internal resistance of 200 ohms of the telephone circuit 4 according to FIG Fig. 1 exceeds the prescribed amount of 220 ohms as indicated above.

Therefore, the circuit shown and described in FIG. 2 cannot be applied remotely local telephone connections because of the large equivalent resistance caused by the voltage drop is caused on the PN connections, the aforementioned conditions are not met.

In the circuit according to FIG. 3 described below, there are corresponding components, such as those with the circuits in FIGS. 1 and 2 are comparable with the same reference numerals. In Fig. are the PNPN transistor switching elements with the reference character 9 provided. However, this circuit has a circuit similar to that of FIG Susceptibility to failure in which C-MOS transistors are used will.

It has also already been proposed in accordance with US Pat. No. 4,060,699 that two-way switching elements be used to bring one of which to four

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paired crossing points is arranged. But this device also has disadvantages insofar as the Telephone exchange relay for remote local telephone subscribers do not work reliably, so that the line lengths of the telephone subscribers to be served are limited, it is also disadvantageous that these switching elements cannot be used in self-holding mode are.

The present invention is therefore based on the object of providing a remedy here. The intercom system is to be improved in such a way that, in connection with conventional keypad devices: becomes usable, as is customary in telephone systems. The telecommunications circuit should be used in conjunction with such keypad devices, the use of telephone subscriber line lengths enable, as is the case with conventional devices *, with the selected speech channel at Interruption of the power supply is kept in operation without the use of additional special measures. In addition, in such a circuit device the polarity on the output side is defined and kept at a certain polarity regardless of

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depending on the power supply polarity of the trunk line or a PBX telephone system and in addition, rectifier bridge circuits for the keypad devices are no longer required are.

It is an object of the invention to provide a voice channel switching device that can be used in conjunction with electronic Touch panel devices is suitable to simplify the circuit structure, so that the manufacturing and service costs can be reduced. It is essential for the invention that the keypad device electronically designed and this can be pre-selected with the exchange lines via the speech channel the circuits can be connected, the invention being essentially characterized in that that the speech channel circuit has two input lines which communicate with two trunk lines stand, and a plurality of output line pairs, which in turn are in connection with a telecommunication circuit of the electronic keypad device, wherein the input lines and the output lines are arranged in matrix form and via device switching elements be controlled and each being a

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such switching element at one of four crossing points between the incoming and the outgoing lines is positioned, and each circuit element with respect to an input line and to an output line which is a Line pair includes, is connected opposite.

The solution to the problem of the invention results from what is stated in the characterizing part of claim 1 Features.

Advantageous further developments and refinements of this solution to the problem can be found in the subclaims.

The present invention is described in more detail below with reference to the accompanying drawings. It means:

Fig. 1 is a block diagram with the individual components of a speech channel of a Prior art keypad device;

Fig. 2 is a connection diagram according to the prior art

the technology for a telephone switch

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circuit using electronic circuit elements with high loss values, such as C-MOS transistors;

Fig. 3 is a circuit diagram of a further embodiment for a Prior art speech channel circuit using electronic switching elements for the on-modulation of the speech current, for example in the middle! PNPN transistors;

Figure 4A

and FIG. 4B are circuit diagrams of a preferred one

embodiment of the invention a speech channel switching device which is suitable for combination with a electronically designed telecommunications circuit;

Fig. 5 is a connection diagram of an embodiment a driver circuit as shown in Fig. 4; and

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6 is a connection diagram of a modified one Embodiment according to the invention.

A preferred embodiment of a speech channel circuit, as shown in Figs. 4A and 4B, is adapted for the use of touch-tone calling systems (key telephone system), in which the common control device is able to Perform switching functions. As FIG. 4A shows, the input terminals Ll and L2 of the central exchange line are the input terminals of the common control device, connected to the ringing signal circuit 12a and 12b, and the outputs of this with the control circuit 13 of the common control device 10. The control circuit 13 can in on be designed in a known manner, for example in the form of a logic circuit or else one stored program control. The input terminals Ll and L2 are one with a switching wiring 20 Speech channel connected, which is an essential feature of the invention. In this circuit arrangement are the lines 21a, 21b, 22a and 22b are connected to the input terminals Ll and L2 and the lines 23a, 23b, 24a and 24b with a touch dial or setting

2942/34

circle, which will be described in more detail below, arranged in matrix form, and in which device PNPN switching elements 25 .. - 25 _{44 are provided} in the form of light-controlled PNPN switching elements, which are located at the crossing points between which the rows and lines of the Matrix prescribing lines lie. Two lines 21a and 21b are in connection with the central exchange line or an office line and the lines 23a and 23b are connected to the telecommunications circuit, so that a corresponding speech loop can be specified when a corresponding switch is actuated. A switching element 25 ^, which connects them lying between the lines 21a and 23a, and a circuit _{element 25 12} as a connecting element between the lines 21b and 23a is in the circuit, so that the current from the exchange lines of the telecommunications circuit when a switching element 25 -, ^ connects the lines 21a and 23b and a switching element 25 _{22 establishes} the connection between the lines 21b and 23b, through this connection a current flows in the opposite direction from the trunk lines to the telecommunications circuit. Within the speech channel switching network 20, a light-emitting diode LED 27a to 27d is provided for each matrix line in order to jointly control the

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Make switching elements of each place in the matrix. For example, the LED diode 27a for the switching elements 25 .. ²⁵ 12 ^'25 21 ^{and 25} 22 is ^responsible for the simultaneous control of these four switching elements through the light emission on the one hand and the extinction of the light emission of the diode 27a.

The LED diodes 27a to 27d are controlled by a driver circuit 28 and according to the control of the control circuit 13 operated. The driver circuit 28 can be of a type known per se, for example of the construction shown in FIG.

If a control signal for the voice channel circuit network is sent from the control circuit 13, then this signal is decoded by means of a decoder 281 and the output of the decoder gives this to the Reference number 282 to the driver transistor, which controls the diode, which is connected to a related drawing intersection point is. The collector of this transistor 282 is through a resistor 283 to a Voltage source V connected, while the emitter of this transistor with the anode of the LED diode 27a communicates.

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The keypad circuit 40 is connected to the main circuit 10, as shown in FIG. 4B. This circuit 40 consists essentially of an electronic speech circuit 41 and a control element 42. The speech channel 41 consists in a known manner from the combination of a hook switch 41a, a turntable or number key multi-frequency signal generator of a transmitter or the like, an electronic Circuit 41b to which a DC voltage should be applied or a current using a Semiconductor element, a noise preventing circuit 41c in the form of a resistor, a Coil and a capacitance and finally a receiver 41d. The speech channel 41, as in Fig. 4B shown corresponds to this, so that the aforementioned reference numerals apply here equally with exception that a rectifier circuit is not provided.

The control element 42 is determined by a sound loudspeaker 42a, an exchange line selection 42b and a control circuit 42c for achieving control in connection with the actuation of a hook switch which interlocks with the key switches 41a and 41b and the control circuit 42c for the operation speakers 42a in accordance with the signal transmission over line 43.

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The control element 42 is of a construction like that described in the article by L.C. Allen et al under the title "Explanatory Common Control Key System Novel Technological Aspects" 7O-CP-253-COM, P. 11-9 11-14, the international communications conference of June 1970 is described. The control element 42 is standing in connection with the control circuit 13 of the common control device 10 via a line 43, which feeds the control data and the operating current to the control circuit, i.e. transmits them to it. In Fig. 4 is only one key 42b of the keypad is shown, there being of course a plurality of such in the device Buttons are provided.

The embodiment shown in Figures 4A and 4B operates as follows: On at A across the terminals Ll and L2 from the telephone exchange in the telephone system incoming ringing signal of 16 Hz, i.e. a signal, which is fed to a distribution center via one of several trunk lines, is in the signal perception circuit 12a recognized as a call signal, so that this circuit a corresponding information the control circuit 13 of the common control device supplies. As a result of obtaining this signal information the common control unit gives a ringing current

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Driver signal to all key fields that are assigned to the common control device. For example this drive signal is input to the control circuit 42 via the line 43 with respect to the keypad 40. The loudspeaker 42a is thus operated via the signal circuit 42c, so that the subscriber knows that a call is being made is present. Accordingly, it is of course also possible to use a lamp instead of the loudspeaker Actuate light signal via control circuit 42c, which is particularly desirable in a telephone system is where a plurality of trunk lines come in connected to a common controller and must be distributed accordingly. When the subscriber to the telephone device presses the selection button 42b the trunk presses and picks up the receiver, then the hook switch contact 41a is closed and thus from the control circuit 42c an information indicating that the user is on the control circuit 13 of the common control device has responded accordingly.

The control circuit 13 of the common control device 10 outputs a selection switching signal to the driver circuit of the circuit elements according to the information given above.

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ORDINAL INSPECTED

As can be seen from FIG. 5, the selection signal is decoded by means of a decoder 281 and is supplied to a selected transistor 282 by means of the driver circuit 28 in order to operate a light-emitting diode 27a. The diode thus emits light which irradiates the connections of the circuit elements 25, 25, 25, 25 and 25 _2. At this time, since the hook switch 41a of the circuit 40 is closed, the light-emitting diode 27a is brought into the light-emitting state and a current loop is established between the telephone circuit 40 and the office terminal. If the switching elements are now exposed to light from the light-emitting diode 27a, then they are biased towards their switched-through state, that is to say conductive. In the event that a positive voltage is applied across the trunk line input terminal Ll and a negative voltage across the input terminal L2, then only the switching elements 25_, and 25, - are biased with respect to the switching elements, namely their crossing points, namely in the forward direction and the other switching elements 25 ,, and 25-- in the opposite direction in this regard. Correspondingly, the current from the telephone system flows through the following circuit components:

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From the input cycle Ll (+) via the line 21a, the switching element 25, ₂₁ , the line 23b, the speech channel 41 (namely a part of this circuit, namely 41c - 41b and 41a), further via the line 23a, the switching element 25, - and back to input cycle L2 (-).

If accordingly a positive voltage across the trunk line input terminal L2 and a negative Voltage is applied to the switching device via the input terminal Ll, then the switching elements 25 ,, and 25__ biased in the forward direction, while the switching elements 25_, and 25. » in the rear or opposite direction are biased, resulting in the following current path from the telephone system results in:

From the input terminal L2 (+) via the line 21b, the switching element 25 ₂₂ , then the line 23b, the speech channel 41 (that is, the part of the circuit 41c, 41b and 41a), then the line 23a, the switching element 25, to to the input terminal Ll (-).

In this way, according to the invention, regardless of the polarity of the voltage source, that is to say the polarity

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the exchange line to the terminals Ll and L2, created the possibility of the current at any time in a defined direction via the telephone device admit. Consequently, the current in each also flows through the electrical circuit 4Ie of the circuit 40 defined direction. In this way it is possible to use the voltage or current supply at any time an exact polarity to provide a multi-frequency signal for the keys of the keypad and to other circuits that require a voltage or current of a defined direction, to circuits that are part of the electronic circuit 41b. This means the fact that when a so-called intercom friend answers, the polarity of the voltage source of the Office is reversed and that the voltage applied to the input terminals Ll and L2 of the exchange line also is swapped, but or if this is the case. or should be, the current flow through the telephone system takes place at any time in a defined direction.

In other words, the invention ensures the possibility of a defined Polarity on the output side on a speech channel switching

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circuit regardless of the polarity of the voltage supplied by the telephone system in a telephone exchange or a PBX telecommunications circuit will. This eliminates the need for the diode rectifier bridge circuit that was previously required.

If one considers the structure of the speech channel, as described above, from the point of view of the rectifier resistance off, then it can be said that due to the fact that the equivalent resistance, i.e. the Equivalent resistance, with a current of 20mA flowing through each of the PNPN circuit elements, is 45 ohms, as stated above, and since two elements are conductively active at each crossing point of the matrix network the total resistance is 90 ohms. The sum total of this resistance is correspondingly the 90 ohm resistance of the speech channel 41, i.e. in detail the sum of the resistances of the components of the circuit 41b (transmitter) and part of the circuit 41c for preventing the crosstalk interference and background noise and a maximum permissible resistance value of 40 ohms for the local lines between the common distribution or control device 10 and the telecommunication circuit 40 at most a value that adds up to 220 ohms, i.e. to

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an amount that is within the prescribed standards. So that lies with this circuit a speech channel distribution, which is also suitable for subscribers of the operations center or the like that are remotely connected to ensure satisfactory conditions.

In the following, the case will be discussed that the operation of the telecommunication circuit normally the existing energy source is suddenly interrupted during the call.

As already stated at the beginning, it was with voice channel switching previously required when using electronic switching elements, such power failures to be bridged by emergency battery systems of relatively large capacity, whereby in connection It should be noted with the present invention that the PNPN circuit elements used here of the voice channel circuit 20 directly from the power source of the office telephone system or Office are fed, so that the falling over the anode and cathode of the PNPN switching elements Voltage holds this switching element self-sustaining in the switched-through state, with this in the

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Go through-connected state when the light-emitting diodes 27a are inactive via the circuit part 27d that ultimately means that these switching elements do not fall back into the non-switched state. After what has been said above, it follows that the speech channel of the telephone control circuit 40 of the Distribution system via the common control device 10 can be kept in the operating state when a Conversation via the control device 10 is ongoing, although the control circuit 13 and the component 42c of the Circuit 40 and the driver circuit 28 of the PNPN switching elements due to the power interruption be inactivated. This means that the system remains functional, so there is no interruption of the call during a power failure without the need for an additional battery or Provide auxiliary power source.

When the connections of a participant by picking up of the handset are operated and so that the fork switch 41a is opened to the DC loop circuit as mentioned above to interrupt, then a corresponding current flows through the switching elements of the Voice channel circuit 20.

0300 "8/0005

ORIGINAL INSPECTED

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In this way, the PNPN switching elements 25_ _lf ²⁵ i2 25 ,,, 25_ _{2 are switched} to the conductive state until the time has expired. The switching function of the speech channel is restored, a relay (not shown) in the telephone system being opened, which enables a limited speech state to be specified.

The circuits using the previously used PNPN switching elements or C-MOS switching transistors were only to be used on the condition that coupling transformers were provided for the Attenuation losses of about 0.5dB in the speech frequency band to get a grip by means of the transformation and thus the transmission quality. To such To keep losses small, it is necessary to use large converters, which is, however, the size of the common distribution system of the telephone device as well as its mode of operation designed uneconomically.

It is therefore an essential part of the invention that the transformer, which is the main part of the Losses caused in the speech channel can be eliminated, so that quality degradations result below 0.05dB, according to the

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AC resistance of the PNPN circuit elements,

As described above, according to the present invention, a voice channel circuit distribution is connected light-emitting components used, the

PN connections of the PNPN circuit elements with that emitted by the light emitting components Light are irradiated, so that said circuit! elements are switched through. It's just supposed to be here It should also be mentioned that such a construction does not apply to certain light-emitting elements or special embodiments is limited. For example, it is possible to use simple gated PNPN transistor switching elements to bring into application.

Referring to Figure 6, there is an alternate embodiment of the voice channel circuit network using gated PNPN circuit elements reproduced, the circuit otherwise corresponding to that shown in FIG. 4a and corresponding components have been provided with the same reference numerals. Since the PNPN switching elements 25 ',, to 25' .. are arranged at corresponding crossing points of the circuit matrix 20 * and, as mentioned, they are gated Is switching elements, there is the opposite to the

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the above-described embodiment modified mode of operation. Corresponding gate connections are with the Cathodes of the gate PNPN switching elements 25 ,, to 25 ..

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via the bias resistors 51 ,, to 51 .., as can be seen from the illustration. In addition, these gate terminals are connected to the cathodes of the diodes 52 1 to 52 ... and the anodes are connected to the driver circuit 28. These diodes are connected so that the mutual effect between the speech channel systems and the control system is reduced and only the driving pulse is applied the gate inputs of the switching elements 25 '., to 25' .. is present. If one considers the switching elements that belong to the arrangement, for example the switching elements 25 ',, and 25, - and the switching elements 25' ₂ , and 25 ', PNPN switching elements 25'., And 25 '.-, the cathodes of which with the central trunk lines are connected, and the PNPN switching elements 25 ', and 25 * 22 » ^whose anodes are connected to the trunk lines, these being connected to the driver circuit 28 in the manner shown. In detail, the anodes of the diodes 52 .. and 52._ are connected together and the anodes of the diodes 52_. and 52_ ₂ also interconnected, each set of interconnected anodes leading to different output terminals of driver stage 28 as shown.

030018/0905

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Of course, other circuit structures are also possible in accordance with FIGS. 4A and 4B.

The modified embodiment according to FIG. 6 operates as follows:

Essentially, the same points of view result here as in the embodiment described above, so if a speech channel switching element is switched to the driver stage 28, then an output signal appears at the associated output terminals a and b of the driver stage 28, so that a connection of the trunk line input A in this way , so the two input terminals Ll and L2 and the distribution circuit 40 can be produced. The output signals obtained are sent to the gated electrodes of the switching elements 25 '^ ₁ and 25' _ and the switching elements 25 '. and 25 'and ₂₂ .. 52. ₂ and 52 ₂₁ and 52 ₂₂ supplied through the diode pairs 52nd Correspondingly, depending on the polarity of the voltage applied to the trunk line inputs Ll and L2, either a pair of switching elements 25 '. and 25 'and 25' ₂ . while another pair is biased in the direction opposite thereto, and the not-connected state is maintained and 25 _'12 biased in the forward direction.

030013/0905

The other operation and effect of the circuit is that of the above-described embodiment same.

03C0 ¹ 8/0905

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Claims (3)

EXPECTATIONS / Iy Circuit arrangement for the speech channel of the switching wiring a telephone intercom using an electronic keypad or in combination with a corresponding dialing device with an electronic speech channel circuit and one connected to this circuit via central trunk lines electronic telecommunication setting device, j characterized in that the speech channel circuit has two input lines connected to two lines of the central exchange line, that a plurality of output I line pairs is connected to the telecommunication setting circuit I of the electronic keypad or the like j network, the Input lines and the output lines are arranged in matrix form, and that in each case a controllable switching element with unilateral directional effect is arranged at each of four crossing points between the input and output lines and each of the switching elements with respect to the corresponding input line and to an output line, which form a line pair, oppositely connected. U-: -M 9/0005 ORIGINAL INSPECTED 2. Circuit arrangement according to claim 1, characterized in that each of the switching elements is a light-controlled component. 3. Circuit arrangement according to claim 1, characterized in that each of the switching elements is a gated block is. 18/09 ^ 5